1. Field of the Invention
The invention relates to a liquid crystal display (LCD) device, and more particularly, to an LCD device having a decreased thickness by providing a light-diffusion member between a lamp and an optical member in a backlight unit.
2. Description of the Related Art
The importance of display devices has recently been emphasized with the development of technology for information communication. In past years, a cathode ray tube (CRT) in this application was widely used. However, the CRT cannot satisfy the latest requirements for the thin profile and lightness in weight. Accordingly, many efforts have been made to research and develop various flat display devices, for example, liquid crystal display (LCD), plasma display panel (PDP), and electroluminescent display (ELD) devices, which can satisfy the requisite of the thin profile and lightness in weight.
Among the above-mentioned flat displays, the LCD device has the most attention owing to the advantageous properties of thin profile, lightness in weight and the low power consumption. Thus, the LCD device is widely used in various applications as a notebook computer, a desktop computer and a large-sized television, and there is the increasing demand for LCD devices.
Generally, an LCD device includes an LCD panel; a driving unit, which drives the LCD panel; and a backlight unit, which supplies light to the LCD panel. The LCD device does not emit light in itself, so that the LCD device necessarily requires an additional light source, for example, a backlight unit to emit light to the LCD panel.
FIG. 1 shows a perspective view of illustrating a related art LCD device.
As shown in FIG. 1, the related art LCD device includes an LCD panel 10 and a backlight unit 20. The LCD panel 10 is composed of first and second substrates 10a and 10b facing each other, and a liquid crystal layer (not shown) provided between the two facing substrates 10a and 10b. The lower substrate 10b includes a thin film transistor (TFT) that functions as a switching element, where the TFT is turned on/off to apply a signal, thereby displaying an image. The LCD panel 10 is connected with gate and source printed circuit boards 15a and 15b, which output video and scanning signals to the LCD panel.
The backlight unit is used as the light source of the LCD device. The backlight unit may be classified into an edge type and a direct type, based on the method of arranging a light-emission lamp. For the edge type, a lamp is positioned at one side or both sides of the backlight unit, and the light emitted from the lamp is supplied to the LCD panel 10 through a light-guiding plate. For the direct type, a lamp is positioned in the LCD panel 10, whereby the light emitted from the lamp is directly supplied to the LCD panel. Generally, the edge type backlight unit is applied to a small-size LCD device, and the direct type backlight unit is applied to a large-size LCD device.
FIG. 1 illustrates the direct type backlight unit 20. Referring to FIG. 1, multiple lamps 21 are positioned under the LCD panel 10. Then, a reflective sheet 22 and a lower case (not shown) are positioned below the lamps 21. In this case, the light emitted from the lamps 21 is supplied to the LCD panel 10 through optical sheets 23. The optical sheets 23 are positioned between the lamp 21 and the LCD panel 10 so as to improve the efficiency of light supplied to the LCD panel 10.
FIG. 2 shows a cross sectional view of illustrating the direct type backlight unit. As shown in FIG. 2, multiple lamps 21 are positioned in parallel, and the reflective sheet 22 is provided under the lamps 21. Also, the optical sheets 23 are formed above the lamps 21. In this case, the optical sheets 23 are composed of a diffusion sheet, a prism sheet and a protective sheet.
However, the related art direct type backlight unit has the following disadvantages.
To uniformly supply the light emitted from the lamp 21 to the LCD panel 23 through the optical sheets 23, as shown in FIG. 3, it is necessary to adjust the value of an interval between the lamp 21 and the LCD panel 23. That is, if the value of interval between the lamp 21 and the LCD panel 23 is too small, portions of the LCD panel will not receive light emitted from the lamp 21. Thus, defects may occur in the LCD panel due to the non-uniformity of the light supply. Also, if the interval between the lamp 21 and the LCD panel 23 is formed above a predetermined value, the thickness of the LCD device increases.